Automatically-operated swinging door structures of various types are well-known and in widespread commercial use. Such door structures are characteristically intended and designed for one-way use with the door swinging away from the entrance side of the doorway toward its exit side. Typically, the swinging operation of the door is electromechanically controlled by actuation from a weight sensitive mat, a photoelectric eye or a similar device for sensing the approach or presence of a person or object requiring opening of the door.
The swinging operation of such doors is recognized to represent a danger or injury to persons at the exit side of the doorway. Therefore, in the past, it has become conventional to utilize a safety mat or a similar sensor to detect the presence of a person or object within the opening path of the door and to prevent the initiation of opening operation of the door under such conditions. Some prior control systems have also incorporated a time delay in conjunction with the safety mat or other sensor to delay deactivation of the safety mat a short time period following each activation thereof. Such time delays serve the two-fold purpose of delaying closing movement of an opened door to permit the pedestrian entering the door from the entrance side to step clear from the safety mat before closing movement of the door begins, as well as to protect a pedestrian on the exit side of the door from opening movement thereof if the pedestrian momentarily shifts his or her weight to a dead spot on the mat or otherwise momentarily deactivates the mat without stepping from it. An example of this type of swinging door control arrangement is disclosed in Boehm U.S. Pat. No. 3,874,117. While such control systems operate effectively for these intended purposes, such systems make no provision for protecting a pedestrian who activates the safety mat after activation of the approach mat has occurred and door opening movement has begun.
As represented by Bond et al U.S. Pat. No. 3,195,879, other swinging door operating arrangements provide for stopping of the swinging door during opening or closing movement when activation of the safety mat occurs. In Bond et al, two safety mats are arranged in series at the exit side of the doorway for this purporse. These control systems also operate effectively in their intended manner but suffer the disadvantage that, when the door is stopped upon safety mat activation, the door is prevented from further opening or closing movement until deactivation of the safety mat.
Other swinging door systems operate to effect closing of the door at substantially any time during the opening operation thereof when the door encounters an object in its swinging path. Eller et al U.S. Pat. No. 4,263,746, discloses an exemplary control system of this type wherein a door-reversing safety arrangement is provided to return the door to its previous closed or open condition at substantially any time the door encounters an object during opening or closing movement, except that a very short time delay is built into the control system to prevent reversal of the door movement during the initiation of each opening and closing movement in order to permit the hydraulic operating system for the door to get underway before the reversing safety arrangement becomes operational. This type of door operating system is considered more disadvantageous than systems of the type of the Bond et al patent in that actual striking contact of the moving door with a pedestrian or other object must occur before door reversal is actuated. Furthermore, the operation of the Eller et al type of system for returning the opening door to its previous closed position at any time after the opening movement is initiated, even when the door is almost fully opened, creates a danger of injury to the person entering the doorway from the entrance side which is at least equal to the danger to the pedestrian or object at the exit side which the Eller et al system seeks to avoid.